Local-overall Interaction Buckling Of High-strength Steel Welded I-section Beam-columns

The slenderness ratio of high strength steel members should not be too large, butthe width-to-thickness ratio of steel plate is relatively large. Therefore, local-overallinteraction buckling is important. For I–section member, local buckling of web doesnot necessarily mean the loss of carrying capacity. In order to achieve the objective ofimproving bearing capacity and saving material, web depth-to-thickness ratio shouldbe relaxed appropriately and post-buckling strength should be used.The ultimate capacity of eccentrically loaded welded I-section members made ofhigh strength steel Q460was analyzed by finite element method. The effects of theweb depth-to-thickness ratio, flange width-to-thickness ratio, slenderness ratio andeccentricity ratio on the local-overall interaction buckling behavior were investigated.Without considering residual stress or the initial geometrical defect for some memberswere re-calculated and analyzed the influence of initial defects on components. Themodified formulas used for predicting the ultimate capacity of high strength steelbeam-columns with large depth-to-thickness ratios were proposed.The study shows that the finite element model presented in this paper cansimulate the nonlinear bucking behaviors of the eccentrically loaded I-shaped memberswith slender web. The ultimate capacity, post-buckling strength reserve and ductility ofthe beam-columns are all increased when the web depth-to-thickness ratio is increased.On the contrary, all are decreased when the flange width-to-thickness ratio increased.The rigidity of the members is obviously reduced resulting in the decrease in theultimate bearing capacity, but the ductility is improved with the increasing of theslenderness ratio. Along with the eccentricity ratio increasing, the flexural deformation dominates the interaction and the deflection at the mid-span increases rapidly, whilethe change in the axial force is relatively slow. The ultimate capacity of members isdecreased for the existence of the initial defects. The proposed modified formulas arein good agreement with the numerical results.